As is known, optical apparatus which employ a zoom lens system generally have at least two lens groups which can be moved relative to each other along a common longitudinal axis during a zooming operation. In such cases, in order to prevent incident light from passing into the space between the two lens groups, light intercepting members have been employed between the two lens groups.
For example, an optical lens system for a zoom camera generally employs a rotation movement lens barrel which is rotated clockwise or counter-clockwise by a driving means as well as a movement lens barrel which is engaged with the rotation movement lens barrel in order to move forward or rearward in response to the rotation of the rotation movement lens barrel. In addition, three lens groups are usually mounted inside the movement lens barrel along the common optical axis. For example, the first lens group is mounted in a first holder which is fixed on the inside of the movement lens barrel to move together with the movement lens barrel, a second lens group is fixedly mounted on a second holder moved by a cam and the third lens group is fixedly mounted on a third holder integrally formed with a hook hooked on a rear end of the movement lens barrel.
It has also been known to provide a spring between the first lens group and the second lens group to maintain a predetermined distance between the two lens groups when the two lens groups move relative to each other to carry out an zooming operation.
Generally, the light intercepting member for intercepting incident light is mounted between the first holder and the second holder. Such a light intercepting member is formed by two or more cylindrical rings inserted in each other to be able to slide between the first holder and the second holder.
In the conventional optical apparatus having a zoom lens, the light intercepting member and the spring are provided in the same space, that is, in the space between the first and second holders. When the zoom lens is in a retracted position, the space is at minimum and when the zoom lens is extended, the space is at maximum. However, when the space is at a minimum (the retracted state), the space cannot be less than the distance equal to the axial length of one of the rings of the light intercepting member.
In the event that the number of rings in the light intercepting member need to be increased in order to increase the maximum length between the two lens groups, it becomes difficult to house both the light intercepting member and the spring in the movement lens barrel.
In addition, since a projection is usually formed on each end part of the rings of the light intercepting member in order to keep the rings inserted within each other during a zoom operation, the external diameter of the light intercepting member becomes relatively large. In such a case, because of the limited space in the zoom assembly, increasing the number of rings of the light intercepting member become very difficult.